In order for a computer to render an image of three-dimensional graphics properly, it needs to determine what objects are in front of others in a scene. A Z-buffer (or “Depth Buffer”) stores a depth value for each pixel of a rendered image, which allows the computer to determine whether each object rendered appears in front of any other object in the scene, on a per-pixel basis.
Because the Z-Buffer only offers a finite amount of precision to store the depth value for each pixel, problems can occur when multiple objects resolve to the same depth value. In addition, the amount of precision varies throughout the 3D scene, as will be described later, so it can be different for the front of the scene and the back of the scene. In particular, the available precision is affected by the choice of the near and far clipping planes for the 3D scene.
Standard systems for generating near and far clipping planes for a 3D scene only consider the bounds of the 3D scene, and ignore the fact that they sacrifice Z-buffer precision as the ratio of near clipping plane distance to far clipping plane distance approaches zero. In addition, systems which only consider the bounds of the scene can suffer from the problem where objects from the very front or very back of the scene can disappear due to precision problems, even though they lie within the near and far clipping plane.